Weird NB matching error in PowerGrids model

[casella]

Please check PowerGrids.Electrical.Test.TwoBusesResistiveTransmissionLineFault. The NB fails with

Error: Internal error NBResolveSingularities.noIndexReduction failed.
(2|2) Unmatched Variables
***************************
        [ALGB] (1) Real transmissionLine.busFault.port.I = Modelica.ComplexMath.'abs'(transmissionLine.busFault.port.i) (start = transmissionLine.busFault.port.IStart, nominal = transmissionLine.busFault.port.IBase)
         slice: {}
        [ALGB] (1) Real transmissionLine.busFault.port.P = transmissionLine.busFault.port.S.re (start = 1e7, nominal = 1e7)
         slice: {}

(1|1) Unmatched Equations
***************************
        [ALGO] (1) ($RES_SIM_0)
[----] when pre(transmissionLine.busFault.fault) then
[----]   transmissionLine.busFault.Y := Complex.'constructor'.fromReal(transmissionLine.busFault.R / (transmissionLine.busFault.R * transmissionLine.busFault.R + transmissionLine.busFault.X * transmissionLine.busFault.X), -transmissionLine.busFault.X / (transmissionLine.busFault.R * transmissionLine.busFault.R + transmissionLine.busFault.X * transmissionLine.busFault.X));
[----] end when;

[----] when not pre(transmissionLine.busFault.fault) then
[----]   transmissionLine.busFault.Y := Complex(0.0, 0.0);
[----] end when;

         slice: {}

This is very weird: I would expect the two variables transmissionLine.busFault.port.I and transmissionLine.busFault.port.P to be matched with their binding equation.

Maybe related to #12239?